ES2707356T3 - Device for holding and deploying devices for use in space - Google Patents

Abstract

A device for holding and deploying devices for use in space, comprising a fixed body (1) and a mobile body (2) coaxially connected to each other in a detachable manner by means of an alloy actuator with memory in a remotely controllable manner , wherein the shape memory alloy actuator consists of a torsion deformable bar (17), wherein the fixed body (1) and the movable body (2) are axially connected to each other by means of coupling members (10 ) movable through said torsion deformable bar (17) from a retention position to couple the movable body (2) to the fixed body (1) to a release position to separate the movable body (2) from the fixed body (1) ), and wherein the elastic means (25, 28) are provided to apply an axial thrust of separation to the movable body (2).

Description

DESCRIPTION

Device for holding and deploying devices for use in space.

Field of the Invention

The present invention relates to devices for securing and deploying apparatus for use in space, such as, for example, solar panels and the like. Devices manufactured in this manner typically include a fixed body restricted to a satellite intended to be placed in orbit, and a mobile body restricted to the apparatus. The mobile body can be deployed or separated from the fixed body through a remote controllable actuator.

State of the prior art

The known clamping and deployment devices of this type generally use, to deploy or separate the moving body from the fixed body, pyrotechnic systems based on the detonation of small explosive charges. These systems reveal one or more of the following drawbacks:

- drive characterized by a high mechanical shock with potential impact on the functionality of the device placed on board the satellite,

- release of contaminating material (solid, liquid or gaseous) and material that could potentially interfere with the optical device on board,

- the control of the preload level is not economic and is subject to elements of uncertainty,

- inability to operate manually,

- provision and use subject to ITAR regulations (satellite export limitations),

- Restart operations that can be carried out only in the facilities of the equipment supplier, with the consequent impact on costs, times and reliability,

- Restart operations that require the replacement of parts of the system, with an impact on costs, times and reliability even in this case,

- limited number of implementations, if not only one.

In order to overcome these drawbacks, it was proposed to replace the pyrotechnic systems with different types of mechanisms, even with the use of shape memory alloy actuators (SMA). Such a solution is described and illustrated in EP-1191271 which provides a remotely controllable retention and release mechanism using, as an alloy actuator of shape memory material (SMA), one or more cables whose Remote controlled heating causes its contraction. Such a contraction frees the rotation of a disc due to which a torsional helical spring is loaded, which normally radially secures the sectors of a nut in which a retaining screw of the apparatus is screwed, which allows, therefore, , the radial opening of the sectors of the nut and the consequent disengagement of the retaining screw. The disk is normally locked in rotation by a crown, driven in rotation by cables made of shape memory material, through retaining balls that can be radially uncoupled from the disk after the rotation of the crown. This solution is not only very complex from the point of view of construction, but also, it is not reliable from a functional point of view.

A similar solution is described and illustrated in JP-H7187094 according to which a nut fastened with a bolt connecting the fixed body to the moving body is formed by two radial portions in which an alloy spiral with memory is wound up. shape. When the spiral is heated, it expands and releases the bolt nut, which allows the separation of the moving body from the fixed body.

Although these solutions overcome some of the problems mentioned above, such as, for example, the uncoupling of the mobile body without releasing material and with relatively low mechanical shocks, its reliability is precarious, even due to the difficulty of efficiently controlling the drive energy .

Another application of a shape memory alloy actuator in the space industry is known from EP-1068447, according to which, in order to control a relative rotation between two elements around a common axis, a bar is provided. alloy torsion with shape memory that has a shape that directly connects such elements. To prevent the relative angle of rotation from exceeding a predetermined critical value, the so-called mechanical fuse configured to break if such an angle is exceeded, is interposed between the torsion bar and one of the elements. This system does not provide or permit controlled separation between the two elements connected by the shape-memory alloy torsion bar.

The known use of a torsion bar as a shape memory alloy actuator for the retention and deployment of spacecraft is also provided in the documents briefly described below.

"SHAPE MEMORY ALLOY REVERSIBLE HINGE FOR DEPLOYMENT APPLICATIONS" - Moignier: this publication refers to a presentation at the 8th ESMATS Conference (European Symposium on Space Mechanisms and Tribologies), held in Toulouse, France, in 1999, which describes the use since 1995 by the French company Matra Marconi Space, of a SMA torsion bar to develop the drive torque required for the deployment of the device space. The document describes the application of the SMA torsion bar and a reversible hinge, with a fixed part and a moving part directly interconnected by the torsion bar.

US-5,975,468 in the name of Matra Marconi Space, published in 1999, also describes the use of an SMA torsion bar as a rotary actuator to move space vehicles from solar panels. Even in this case, the torsion bar is connected directly to the mutually rotating parts, through thermally insulating interface end elements.

Furthermore, US-6,065,934 in the name of The Boeing Company published in 2000 discloses a rotary actuator for aerospace applications formed by a tubular rod with an associated superelastic return spring.

US-4,798,051 on behalf of The Boeing Company published in 1989 probably chronologically represents the first document showing the use of an SMA torsion bar as a rotary drive means, which considers the operation field of the company and the field in which the company that owns the patent then operated, for use in the aerospace industry.

Summary of the invention

The object of the present invention is to provide a device for holding and deploying apparatus for use in space that is not only capable of overcoming the drawbacks revealed by the pyrotechnic systems, but also allows the optimum exploitation of the characteristics of the materials of alloy with shape memory in a safe and reliable way, with particularly small overall dimensions and specially configured to be reused for several drives.

According to the invention, this objective is achieved mainly through a clamping and deployment device of the type defined in the pre-characterization part according to claim 1, and generally corresponds to the prior art represented by the aforementioned US Pat. No. 5,975,468 above, characterized in that the fixed body and the movable body are connected axially to each other via the displaceable coupling members through said deformable torsion bar from a detent position to couple the movable body to the fixed body to a release position. to separate the moving body from the fixed body under the action of the axial thrust elastic means.

According to a preferred embodiment of the invention, the fixed body includes a rotating reel driven in rotation by the deformable torsion bar, and the bar is twisted to such a spool in a unidirectional manner, only in the direction of rotation corresponding to the release of the coupling members, but not in the opposite direction.

According to a further advantageous feature of the invention, the elastic axial thrust means acting on the mobile body comprise a preload spring and a start-up spring independent from each other and with differentiated action. The preload spring is configured to apply to the moving body a greater axial force for a short stroke, while the start-up spring is configured to apply a lower axial force to the moving body for a longer stroke compatible with its separation in relation to the fixed body.

Thanks to the features mentioned above, along with others that will be detailed below, the clamping and deployment device according to the invention allows to obtain the advantages listed below:

- uncoupling the mobile body without generating mechanical shocks and without releasing materials,

- possibility to visibly indicate the applied preload,

- possibility to operate manually,

- automatically executable clamping function,

- restoration operations (returning the release condition to the holding condition after a device release operation) in a simple and fast manner, without having to disassemble or replace the components,

- small overall axial dimension of the device as a whole and, consequently, ease of installation in the limited space usually available between the satellite and the panel,

- high drive repeatability.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in detail with reference to the accompanying drawings, provided purely by way of non-limiting example, wherein:

- Figure 1 is a general perspective view of the fastening and deployment device according to an embodiment of the invention, represented in the coupled configuration of the mobile body with respect to the fixed body,

Figure 2 is an axial sectional view showing the device in the released condition of the moving body, - Figure 3 is a perspective view of the section of Figure 2; rotated 180 °,

- Figures 4 and 5 are perspective views exemplifying the operation of a torsionally deformable SMA bar, - Figure 6 is an exploded perspective view of part of the fixed body of the device,

- Figure 7 shows two components of Figure 6, on a larger scale,

- Figure 8 is a top perspective view, simplified and on a larger scale, of part of the fixed body,

- Figure 9A illustrates two components of Figure 6, in greater scale and detail,

- Figure 9B is a back view of Figure 9A,

- Figure 10 is a dorsal perspective view of two components of Figure 6,

- Figure 11 is a perspective view of the mobile body of the device, on a smaller scale,

- Figures 12, 13 and 14, 15 are schematic views, respectively in cross section and in axial section, which exemplify the decoupling of the moving body from the fixed body of the device,

- Figure 16 is a perspective and enlarged view of an additional component of the device, and

- Figures 17 and 18 are diagrams that exemplify the mode of operation of the device according to the invention.

Detailed description of the invention:

The mode of the device for holding and deploying the apparatus for use in the space represented in the drawings essentially comprises a fixed body 1 and a mobile body 2 connected coaxially to each other in a detachable manner and provided with the respective flanges 3, 4, for example , for fixing to a satellite and a solar panel. The fixed and mobile bodies 1, 2 are kept integrally joined to each other in the launching and orbiting stages, as shown in Figure 1, and are therefore uncoupled to allow the deployment of the solar panel.

The fixed body 1 comprises a substantially cylindrical retaining cable element 5 whose end portion 6, opposite the flange 3, is formed on its side wall with a radially spaced crown of equally spaced 7 holes.

In such an end portion 6 of the retention element 5, a hollow reel 8 formed with a crown of cavities 9 equally angularly spaced like the radial holes 7 is coaxially inserted. A ball crown 10 cooperates with the holes 7 and the recesses 9 as described in more detail below: As can be seen below, such balls 10 constitute engaging members movable from a holding position to a releasing position of the moving body 2 due to controlled rotation of the spool 8 about the axis of the device.

An actuator body inserted coaxially in the spool 8 and coupled thereto in rotation through the respective drive planes 12, 13 is indicated in its entirety with 11 (Figure 7).

The spool 8 can rotate in the portion 6 of the retention element 5 for an angular field limited by the coupling between a radial tooth 14 of the reel 8 and a cavity 15 formed in the portion 6 (Figure 10).

The actuator body 11 has centrally a square through hole 16 in which a complementary end 17a of a cylindrical bar made of material SMA 17, for example, a nickel-titanium alloy, which extends coaxially through the retaining element 5 and whose opposite end 17b is anchored to a lower part 18 (Figures 2 and 3). Such a bar SMA 17 constitutes the remotely controllable actuator for obtaining the controlled separation of the mobile body 2 from the fixed body 1.

A twisting helical spring 39, the function of which will be clarified below, surrounds part of the SMA bar 17 and is anchored at its ends, respectively, to the reel 8 and to the lower part 18.

A fifth sliding wheel applied to the end portion 6 of the retaining element 5 and against which the spool 8 slides during its rotation is indicated by 19. The fifth wheel 19 is locked in rotation with respect to the retaining element 5 through of a radial tooth 20 coupled in a cavity 21 of the end portion 6 (FIG. 8) and, in turn, has an interior angular cavity 22 through which a radial tooth 23 of the actuator body 11 engages (FIGS. 9A and 9B) to limit the angular rotation field of such body 11 from a reset position.

A sleeve with a thrust function arranged coaxially outside the retention element 5 and axially movable with respect to the latter is indicated by 24 (Figures 1-3). Such thrust sleeve 24 is subject to the action of two different elastic members independent of each other and with differentiated action. The first elastic member consists of a preload spring 25, shown in detail in FIG. 16, formed by a corrugated elastic ring interposed between an annular flange 26 integrally connected to the retaining element 5 and an annular preload nut 27 transported axially adjustable by the push member 24. The second elastic member consists of a pack of Belleville washer 28 with a start-up function interposed between the push member 24 and the retaining element 5.

The load developed by the preload spring 27 can be selected and visually identified through the angular position of the annular nut 27: in particular, the maximum load corresponding to the total deformation of the spring 25 is achieved through a rotation of the nut annular 27 equivalent to one revolution, so that a positioning error, for example, of 10 ° with respect to the visual objective, leads to a pre-load variation applied below 3%.

The preload spring 25 is capable of applying to the thrust member 24 a relatively high axial load (for example, of the order of 4000 N) with a limited axial stroke (for example, of the order of about 1 mm), while the spring of start-up 28 is configured to apply a lower axial force to the thrust member 24, but for a larger axial stroke. These effects and the relative advantages will be described in more detail below.

Figures 4 and 5 schematically exemplify, with reference to a simple SMA prismatic bar with constant square section 17, the operation of the alloy bar with shape memory 17. As is known, shape memory alloys represent a class of materials Metals in which there is a transformation from phase to solid phase (that is, in which both the initial phase and the final phase are solid structures, albeit with different crystallographic patterns) called thermoelastic martensitic transformation. In particular, its main characteristic resides in being able to recover a pre-established macroscopic shape due to the simple change of temperature or applied stress state.

According to the invention, the SMA bar 17 is deformable by twisting: it is subjected to a specific torsional deformation at room temperature in advance under martensitic conditions, as outlined in Figure 5. Therefore, bar 17, after of the transformation of the martensitic phase to the austenitic phase obtained by heating it to a temperature higher than the phase transformation, returns to the normal non-deformed condition schematized in Figure 4, which recovers the deformation by previous torsion established in the conditions martensitic

The heating is obtained due to the Joule effect, through a normal heater, for example, integrated directly into the SMA bar 17 and provided with a circuit to limit the absorbable power, of the generally conventional type and, therefore, not described in detail in the present description, capable of preventing phenomena of overheating and excess consumption of electrical energy. The heater can be easily controlled remotely in an equally conventional manner.

As can be seen below, the torsional deformation induced in the SMA bar 17 controllably rotates the body of the actuator 11 and, therefore, the spool 8, against the action of the torsion spring 39 and for a limited angular width. delimited by the cavity 15 in which the tooth 14 is movable, as well as by the cavity 22 of the sliding fifth wheel 19 in which the tooth 23 of the body of the actuator 11 can move.

The mobile body 2, illustrated in its entirety in Figure 11, has an annular configuration and, in the coupling condition shown in Figure 1, coaxially surrounds the end portion 6 of the retention element 5. The base of the movable body 2 it is formed in an annular inclined groove 29 so as to have a ring of cavities with a spherical-cylindrical surface 30 angularly spaced equally to reduce the state of hertzian tension induced in the movable body 2 of the balls 10.

In the coupling condition of the device shown in Figure 1, the movable body 2 is locked axially with respect to the fixed body 1 due to the coupling carried out by the balls 10, as schematized in Figures 12 and 13. In such condition , the movable body 2 is fastened, through the push member 24, to the action of the preload spring 25 and the start springs 28. When the coupling action carried out by the balls 10 is eliminated, as shown in FIG. explained and schematized later in Figures 14 and 15, the moving body 2 is not restricted axially from the fixed body 1 and is uncoupled therefrom by the axial thrust exerted by the pushing member 24.

The operation of the fastening and deployment device according to the invention will now be described in detail.

As mentioned above, in the coupling condition shown in Figure 1 and schematized in Figures 12 and 13, the balls 10 are maintained in a coupling position radially withdrawn between the spool 8 and the mobile body 2: the angular position of the The reel 8 is in this case so that the recesses 9 are offset angularly with respect to the balls 10, which project partially from the holes 7 of the end portion 6 of the retaining element 5, which rest on the inclined surface 29 of the movable body 2. This condition, in which the SMA bar 17 is deformed in a martensitic manner and is not subject to any stress, is maintained by the action of the twisted helical spring 39. The inclined surface 29, pushed against the balls 10 by the action of the preload spring 25 and the start-up spring 28, apply an axial and radial load component to such balls 10.

To obtain the decoupling and separation of the movable body 2 from the fixed body 1, that is, the condition shown in Figures 2 and 3, the heater of the SMA bar 17 is operated remotely, to cause thermoelastic martensitic transformation and, therefore, the opposite deformation by torsion of the SMA bar 17 towards the initial shape not deformed. Due to such torsional recovery, the torque applied by the SMA bar 17 to the body of the actuator 11 is transmitted by the latter to the reel 8 which rotates from the angular position shown in Figure 12 to that illustrated in Figure 14, in which the cavities 9 are aligned with the balls 10. Therefore, the balls 10 move radially from the extracted position to the recessed position in which they disengage from the inclined surface 29 of the mobile body 2. This radial recession of the balls 10 , facilitated by the radial component of the thrust exerted by the pushing member 24 transmitted by the inclined surface 29, leads to the separation of the mobile body 2 from the fixed body 1 under the action of the preload spring 25, which, as mentioned, develops a high spring force for a very short stroke, and the spring running 28 that applies a load of less intensity but that works for a race compatible with the complete uncoupling of the mobile body 2.

In this step, the combined effect of the torsional deformation of the bar 17, which allows controlling the rotational movement of the reel and, therefore, the radial return displacement of the balls 10, and the differentiated action of the springs 25 and 28 allows to effectively eliminate the generation of mechanical shocks: the diagram of Figure 17 represents the relationship between the displacement of the balls 10, respectively in the radial direction with continuous line and in the axial direction with dashed line, as a function of the rotation applied to the spool 8 due to the deformation of the SMA bar 17.

The graph of Figure 18 represents the relationship between the radial movement of retraction of the balls 10 and the axial thrust of separation applied to each ball 10 by the springs 25 and 28. As can be observed in this second diagram, the absence of shock in the maximum elongation of the starting spring 28 is ensured by the fact that the preload spring 25 exhausts its thrust long before the SMA bar 17 and the controlled balls 10 exhaust theirs, thus avoiding the appearance of impact phenomena. This advantageous effect is also a direct consequence of the relative slowness with which the SMA bar 17 recovers its non-deformed state, during the austenitic transformation thereof. Furthermore, since the restriction between the SMA bar 17 and the spool 8 described above is unidirectional, that is, it is configured to execute the mutual torsional coupling only in the direction corresponding to the release of the movable body 2, the SMA bar 17 can returning to preform to prepare it for a new opening without affecting the state of the device, in particular with the mobile body 2 in the engaged position. Basically, this allows carrying out the restoration operation in the SMA bar 17 on the ground and manually operating the device, to open and close, without modifying the state of such SMA bar 17. This also allows, advantageously, to restart the device and installed on board the satellite, without replacing parts and in a simple and fast way, by acting on the operating point obtained on the reel 8 and externally accessible, indicated with 31 in Figure 1.

An additional advantage of the clamping and deployment device according to the invention lies in the possibility of using it potentially for a large number of drives.

Obviously, the construction details and embodiments may vary widely with respect to what is described and illustrated, without departing from the scope of protection of the present invention as described in the claims that follow.

Claims (12)

Claims A device for holding and deploying apparatus for use in space, comprising a fixed body (1) and a mobile body (2) connected coaxially to each other separable by means of an alloy actuator with controllable shape memory at a distance, wherein the shape memory alloy actuator consists of a torsionally deformable bar (17), wherein the fixed body (1) and the mobile body (2) are connected axially to each other by means of coupling members (10) displaceable through said torsionally deformable bar (17) from a holding position to couple the moving body (2) to the fixed body (1) to a release position to separate the moving body (2) from the fixed body (1), and wherein the elastic means (25, 28) are provided to apply an axial thrust of separation to the moving body (2). The device according to claim 1, characterized in that the fixed body (1) includes a rotating reel (8) driven in rotation by said torsionally deformable bar (17) to allow the displacement of said coupling members (10) from the hold position to the release position. The device according to claim 2, characterized in that said coupling members (10) are constituted by a ring of balls (10) designed to move from a radially extracted position to a radially retracted position relative to the spool (8) . The device according to claim 3, characterized in that the reel (8) is formed by a crown of cavities (9) that in a first angular position, corresponding to a geometry of said torsionally deformable bar (17) obtained afterwards. of their torsional deformation under martensitic conditions are shifted angularly with respect to said balls (10) which are maintained in said radially extracted condition, and in a second angular position corresponding to said torsionally deformable bar (17) which has recovered a condition not deformed after their austenitic transformation, they are angularly aligned with said balls (10) disposed in said radially retracted condition. The device according to claim 4, characterized in that said torsionally deformable bar (17) is twisted to said reel (8) in a direction corresponding to the rotation thereof from said first angular position to said second position. angular but not in the opposite direction. The device according to claim 4, characterized in that in said condition radially retracted the balls (10) rest against an annular inclined surface (29) of the moving body (2) configured in this way to apply said balls (10) the thrust of said elastic means (25, 28) according to an axial component and a radial component. The device according to claim 6, characterized in that said annular inclined surface (29) is provided with cylindrical spherical cavities (30) designed to reduce the state of hertzian tension induced by said balls (10) to the moving body (2) . The device according to one or more of the preceding claims, characterized in that said elastic means comprise a preload spring (25) and a start-up spring (28) independent of each other and providing a differentiated action. The device according to claim 8, characterized in that said preload spring (25) is configured to apply a greater axial force during a short stroke to the moving body (2), and said start-up spring (28) is it configures to apply to the moving body (2) a lower axial force for a longer stroke compatible with the separation of the moving body (2) from the fixed body (1). The device according to claim 9, characterized in that the preload spring consists of a corrugated elastic ring (25) interposed between an annular flange (26) of the fixed body (2) and an outer annular nut (27) applied from adjustable manner to an axial thrust member (24) acting on the movable body (2). The device according to claim 9, characterized in that the start-up spring consists of a pack of Belleville washers (28). The device according to any of the preceding claims, characterized in that said torsionally deformable bar (17) incorporates a remotely controlled Joule effect heater designed to operate the thermoelastic martensitic transformation of said bar and provided with a circuit to limit the power that can be absorbed to inhibit the phenomena of overheating and excessive consumption of electrical energy.